Understanding crystallinity in aromatic polyimides

Aromatic polyimides are a class of polymers that show remarkable thermal stability, strength, and toughness. These properties make them attractive candidates for use in high-performance carbon fiber composites for airborne and spaceborne structural components. Our research centered on the development of an understanding of the underlying process of crystallite formation in a particular class of aryl polyimides for which there are some x-ray crystallographic data available. The ultimate aim of the project is to be able to develop a model sufficiently flexible to be able, on the basis of the chemical structure of a polymer in this class, to predict: (1) whether it will be prone to form crystallites; (2) crystallographic features of the crystallites; and (3) synthesis and/or processing conditions that will be favorable or unfavorable to crystallite formation. This will provide guidance to the laboratory chemists in their choice of candidate polymers and processing methods

Mise en évidence et caractérisation de trois séquences répétées au sein de : Coffea pseudozanguebariae Bridson et Coffea liberica var. dewevrei De Wild et Th. Dur.

Afin d'étudier les possibilités offertes par l'hybridation interspécifique chez #Coffea canephora, un croisement modèle entre deux espèces phylogénétiquement éloignées est étudié : #C. canephora (PSE) x #C. liberica var. #dewevrei (DEW), proche de #C. canephora. La quantité d'ADN nucléaire des deux espèces est respectivement de 1,13 pg et de 1,43 pg. Elle peut s'expliquer par des différences de constitution chromosomique principalement au sein de séquences non codantes, essentiellement répétées. La construction d'une banque a été préférée à des méthodes plus sélectives de façon à couvrir le génome en entier. A partir d'une banque d'ADN génomique d'hybride F1 restreint aux site GATC, par l'endonucléase Sau3A, 193 clones contenant des séquences répétées ont été retenus, après rétrohybridation. Vingt deux sondes sont totalement séquencées, 5 partiellement. Elles sont riches en AT et montrent souvent des sites GATC internes. La plupart ne présente pas d'homologie avec les séquences connues. Trois sondes sont analysées de façon plus approfondie sur les espèces parentes PSE et DEW et sur 8 autres espèces choisies pour leur origine géographique et leur quantité d'ADN (#C. racemosa, #C. sessiliflora, #C. eugenioides, #C. sp "#Moloundou", #C. canephora, #C. congensis et #C. heterocalyx$). La première est constituée de quatre séquences distinctes, dont une au moins répétée en tandem. La seconde révèle une forte homologie avec des séquences codant pour la reverse-transcriptase de rétrotransposon de type gypsy-like, tant au niveau nucléotidique qu'au niveau acides aminés. Elle est donc, le premier rétrotransposon découvert chez les caféiers. La dernière possède des profils RFLP sur l'ADN différents uniquement pour les deux espèces à forte quantité d'ADN. Il est primordial de poursuivre l'étude du rétrotransposon pour préciser son nombre de répétitions, sa structure fine et sa capacité à transposer... (D'après résumé d'auteur

Satellite Measurements of the Angstrom Exponent using an Innovative Mathematical Method to Identify Seasonal Aerosols

The remote sensing methods for understanding physical phenomena are being used since the last 50 years. Satellite- based sensors and ground-based sun photometers provides quantitative and qualitative knowledge about the composition of elements within the Earth’s atmosphere. One actual problem is the changes on the climate of different regions of the Earth; one of them is related to aerosol climate forcing. Improvement in measurement-based systems is necessary to identify remaining issues and improve quantification of aerosol effects on climate. Also the improvement in modeling is necessary to confidently extend estimates of forcing to prior times and to project future emissions. Achieving these capabilities will require a synergistic approach between observational systems and modeling. This paper describes how the study and analysis of satellite-based and ground-based measurements can be used to develop an innovative method, based in the existent methods to calculate some optical properties that will help in characterization of the dominant temporal aerosols found in and around the city of Guadalajara in Mexico, based on previous algorithms. The quantifiable knowledge about the temporal and regional aerosols’ optical properties will contribute to future investigations related to their quantitative effects on atmospheric processes in this region.ITESO, A.C.Universidad de GuadalajaraNASA Goddard Space Flight Cente

Biases in Long-term NO2 Averages Inferred from Satellite Observations Due to Cloud Selection Criteria

Retrievals of atmospheric trace gas column densities from space are compromised by the presence of clouds, requiring most studies to exclude observations with significant cloud fractions in the instrument's field of view. Using NO2 observations at three ground stations representing urban, suburban, and rural environments, and tropospheric vertical column densities measured by the Ozone Monitoring Instrument (OMI) over each site, we show that the observations from space represent monthly averaged ground-level pollutant conditions well (R=0.86) under relatively cloud-free conditions. However, by analyzing the ground-level data and applying the OMI cloud fraction as a filter, we show there is a significant bias in long-term averaged NO2 as a result of removing the data during cloudy conditions. For the ground-based sites considered in this study, excluding observations on days when OMI-derived cloud fractions were greater than 0.2 causes 12:00-14:00 mean summer mixing ratios to be underestimated by 12%+/-6%, 20%+/-7%, and 40%+/-10% on average (+/-1 standard deviation) at the urban, suburban, and rural sites respectively. This bias was investigated in particular at the rural site, a region where pollutant transport is the main source of NO2, and where longterm observations of NOy were also available. Evidence of changing photochemical conditions and a correlation between clear skies and the transport of cleaner air masses play key roles in explaining the bias. The magnitude of a bias is expected to vary from site to site depending on meteorology and proximity to NOx sources, and decreases when longer averaging times of ground station data (e.g. 24-h) are used for the comparison

Development of a Novel Algorithm to Calculate the Optic Properties of Temporal Aerosols Through Remote Sensing Data Measurements: Prospective Study

Satellite’ sensors as well as ground-based sun photometers instruments surface are utilized gather data about the quantitative composition of components in the Earth’s atmosphere. The relationships among these components produce effects in different phenomena, like regional climate change. Aerosols, consisting of particles from 0.01 to 10 m, are atmosphere components, whose effects are still poorly understood. Through Remote Sensing, it is possible to classify them and gain information about their role in different atmospheric processes: low visibility, solar energy balance, cloud formation and increases or decreases of the quantity of precipitation. This paper describes how the study and analysis of satellite-based and ground-based measurements can be used to develop and validate a novel procedure to calculate the optical properties of temporal aerosols found in and around Guadalajara, based on previous algorithms:, to determine the aerosol size distribution function, scattering phase function, single scattering albedo, complex refractive index and asymmetry parameter. The quantifiable knowledge about the temporal and regional aerosols’ optical properties will contribute to future investigations related to their quantitative effects on atmospheric processes in this region. These effects include: alteration of weather and climate, change of the tropospheric temperature, contribution to environmental ills, the formation and properties of the clouds, effects on the ecosystems, local solar energy balance, and the impacts on human health.ITESO, A.C.ITESMNASA Goddard Space Flight Cente

The Sensitivity of U.S. Surface Ozone Formation to NOx, and VOCs as Viewed from Space

We investigated variations in the sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NO(x)) as inferred from the ratio of tropospheric columns of formaldehyde and nitrogen dioxide from the Aura Ozone Monitoring Instrument (OMI). The data indicate that ozone formation became: 1. more sensitive to NO(x) over most of the U.S, from 2005 to 2007 because of substantial decreases in NO(x) emissions primarily from stationary sources, and 2. more sensitive to NO(x) with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. Based on our interpretation of the data, current strategies implemented to reduce unhealthy levels of surface ozone should focus more on reducing NO(x) emissions, except in some downtown areas which have historically benefited from reductions in VOC emissions

Using Satellite Remote Sensing and Modelling for Insights into N02 Air Pollution and NO2 Emissions

Nitrogen oxides (NO(x)) are key actors in air quality and climate change. Satellite remote sensing of tropospheric NO2 has developed rapidly with enhanced spatial and temporal resolution since initial observations in 1995. We have developed an improved algorithm and retrieved tropospheric NO2 columns from Ozone Monitoring Instrument. Column observations of tropospheric NO2 from the nadir-viewing satellite sensors contain large contributions from the boundary layer due to strong enhancement of NO2 in the boundary layer. We infer ground-level NO2 concentrations from the OMI satellite instrument which demonstrate significant agreement with in-situ surface measurements. We examine how NO2 columns measured by satellite, ground-level NO2 derived from satellite, and NO(x) emissions obtained from bottom-up inventories relate to world's urban population. We perform inverse modeling analysis of NO2 measurements from OMI to estimate "top-down" surface NO(x) emissions, which are used to evaluate and improve "bottom-up" emission inventories. We use NO2 column observations from OMI and the relationship between NO2 columns and NO(x) emissions from a GEOS-Chem model simulation to estimate the annual change in bottom-up NO(x) emissions. The emission updates offer an improved estimate of NO(x) that are critical to our understanding of air quality, acid deposition, and climate change

DISCOVER-AQ: An Overview and Initial Comparisons of NO2 with OMI Observations

The first deployment of the Earth Venture -1 DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) project was conducted during July 2011 in the Baltimore-Washington region. Two aircraft (a P-3B for in-situ sampling and a King Air for remote sensing) were used along with an extensive array of surface-based in-situ and remote sensing instrumentation. Fourteen flight days were accomplished by both aircraft and over 250 profiles of trace gases and aerosols were performed by the P-3B over surface air quality monitoring stations, which were specially outfitted with sunphotometers and Pandora UV/Vis spectrometers. The King Air flew with the High Spectral Resolution Lidar for aerosols and the ACAM UV/Vis spectrometer for trace gases. This suite of observations allows linkage of surface air quality with the vertical distributions of gases and aerosols, with remotely-sensed column amounts observed from the surface and from the King Air, and with satellite observations from Aura (OMI and TES), GOME-2, MODIS and GOES. The DISCOVER-AQ data will allow determination of under what conditions satellite retrievals are indicative of surface air quality, and they will be useful in planning new satellites. In addition to an overview of the project, a preliminary comparison of tropospheric column NO2 densities from the integration of in-situ P-3B observations, from the Pandoras and ACAM, and from the new Goddard OMI NO2 algorithm will be presented

A New Species of Tradescantia (Commelinaceae) from South Texas

This taxon first came to the attention of the author as the result of a collection of two plants from the Edwards Plateau by C. M. Rowell. Both of these plants died shortly after being transplanted, due to the long exposure they had received, but not before a few morphological notes had been taken. Later, in the spring of 1950, I encountered a small population in the Edwards Plateau of Texas between Burnet and Llano, along the roadside of State Highway 29 near Buchanan Dam. This was approximately fifty miles from the locality of the collection made by Rowell. The population consisted of 25 to 30 quite distinct plants, and on the same general site there was a much larger population of Tradescantia gigantea Rose. Although both taxa were flowering prolifically there were no plants found that indicated hybridization between the two. There appears to be little doubt that this taxon is the same material that was referred to by Anderson & Woodson (1935) as a putative hybrid between T. humilis and T. occidentalis. Both of these species are diploids in South Texas with 12 somatic chromosomes. However, in our material, plants with eglandular hairs on the sepals have not been found. It was mentioned by Anderson & Woodson that this taxon appears difficult of solution, and they point out that B. C. Tharp feels that it seems to constitute a recognizable element of the flora, and that Anderson is inclined to agree on the basis of breeding and cytological data. However, Woodson feels that it is definitely intermediate between the two supposed parents. It seems obvious from these statements that more experimental data were needed before the problem could be solved, and this report is the result of such a study

Chronicles of Oklahoma

Article chronicles the public's opinions and reactions to desegregation throughout Oklahoma by analyzing editorials and newspapers published during three major Supreme Court Cases: Sipuel v. Board of Regents of the University of Oklahoma, McLaurin V. Oklahoma Stage Regents, and Brown v. Board of Education